The invention relates to a device for stacking sheets, especially sheets of paper that arrive overlapped.
A method of and device for replacing a stack of sheets without interrupting the supply of sheets to the stacking point is known from Application Ser. No. 938 206, now U.S. Pat. No. 4,796,897. The full stack can be replaced without losing any sheets and without the sheets being displaced during the replacement.
This device features means of conveying the overlapping sheets to a stacking point accommodating a layoff platform that can be raised and lowered. Behind each stack are a separating mechanism that travels up and down and consists of a pivoting arm with a sheet-metal separator on its free end, two compression jaws that are positioned at different levels and travel up and down and along the direction that the sheets are conveyed in, and an auxiliary stacking platform that can be both displaced along the direction that the sheets are conveyed in and lowered. The separating mechanism that moves up and down can be inserted between the rear edges of the sheets at the top of the stack, especially between the uppermost sheet on the stack and the stream of overlapping sheets. The separating mechanism and the compression jaws are in the form of laterally separated forks or grates, so that the compression jaws on the separating mechanism can travel between them.
When a stack is replaced, the compression jaws enter the gaps created by the separating mechanism between the rear edges of the sheets and compress a pack of sheets, whereas the auxiliary stacking platform is introduced or retracted. The upper part of the stack rests on the auxiliary stacking platform while the bottom part of the stack is removed.
The method of replacing a stack in accordance Application Ser. No. 938 206 also has other advantages.
Since the upper sheets of the stack being removed are preliminarily pressed down and hence have the air pressed out of them, the stack is ready to move without the uppermost sheets flying off.
The sheets can be stacked on a pallet with edges projecting from each side, so that, once protective corners have been added to the top, the stack can be secured on the pallet with straps without damaging the edges of the sheets.
Since the pack of sheets is secured stationary while the auxiliary stacking platform is being introduced and retracted, the sheets will not be mutually displaced in the vicinity of the platform and their lateral surfaces will remain straight.